1. Technical Field
An embodiment of the invention relates generally to the fabrication of integrated circuits, and in particular relates to the processing of a resist layer in the fabrication of integrated circuits.
2. Description of the Related Art
Resist layers (sometimes called photoresist layers to imply the lithographic processes typically used with them) are frequently used to generate masks during the fabrication of integrated circuits. A layer of resist material is deposited on the surface of an underlying layer to be patterned. The layer of resist material is then exposed to light in a specific pattern, and processed in a way that removes the exposed portions of the resist material (or alternately removes the non-exposed portions) so that the remaining resist material forms a mask in the shape of the exposure pattern. The areas of underlying material that are not directly covered by the mask are then removed through an etch process, such as a plasma etch, with the mask of resist material preventing removal of those portions of the underlying material that are directly under the resist material. The mask of resist material is then removed through another process, leaving only those portions of the underlying layer that form the shape of the original pattern.
Because an etch is a destructive process, the etch may also cause deterioration of the resist material. This deterioration may uncover additional portions of the underlying material before the etch is complete, thereby etching portions of the underlying material that were intended to be protected from the etch process. The deterioration is typically greatest at the edges of the resist material, so that small-geometry elements such as transistor gates may be significantly reduced in size when the edges of the resist pattern that creates those elements are unintentionally etched away. Regardless of geometry, resist material designed for exposure light with a wavelength of approximately 193 nanometers (nm) is particularly susceptible to deterioration during the plasma etch.
Resist material may be hardened against this deterioration by curing the resist material with an electron beam before the plasma etch process. However, electron beam tools are generally expensive and too slow for high volume manufacturing, and are not available in many integrated circuit fabrication facilities.